1. Field of the Invention
The invention relates to manufacture of a flexible recording disk of the type used in a digital data storage unit. More particularly, the invention relates to apparatus for positioning and attaching a reinforcing ring about a spindle drive aperture of the disk.
2. Description Relative to the Prior Art
In the following description of the relevant prior art, reference is made to FIG. 1, of the accompanying drawings, which shows apparatus, known in the art for positioning and attaching a reinforcing ring about a spindle drive aperture of a flexible recording disk.
A "floppy disk" assembly includes an envelope enclosing a disk of flexible material such as polyethylene teraphthalate ("PET"). A material including magnetic particles, preferably ferric oxide (Fe.sub.2 O.sub.3), covers one or both surfaces of the disk. The disk has a central aperture made precisely to rigid standards for fitting upon an output spindle of a disk drive mechanism. Likewise, the envelope has apertures therethrough for receiving the spindle, for indexing, and for receiving a read/write head of the drive mechanism for transferring information to and from the data storage area of the floppy disk. U.S. Pat. No. 3,668,658, issued to Flores, et al., discloses a method of constructing a floppy disk assembly.
One of the primary problems encountered in the use of a floppy disk is the centering of the disk precisely on the spindle of the drive mechanism. Centering is of extreme importance because it is necessary that the same data be at exactly the same position with respect to the read/write head and an index point each time the disk is placed upon the spindle. If the disk is not precisely centered, indexing for the read/write head will not operate in an optimum manner. Variations in the centering of the disk may make it necessary for the read/write head to scan a wider area or track, to find the desired information. This limits the number of tracks, and thus the amount of data, which can be recorded on a given disk.
The problem with centering the disk is further complicated because the drive spindle subjects the material immediately surrounding the central aperture of the disk to stress forces during both insertion of the disk into the drive mechanism and rotation of the disk within its envelope. It is known in the prior art that these stress forces may damage the central aperture of the disk. Ultimately, this damage may become so extensive as to render the disk totally inoperable. Even if such damage is not so severe, it may be, however, the source of misalignment between the drive spindle and the disk, thereby causing data reading failures.
A variety of prior art attempts has dealt with strengthening the central aperture of the disk, to extend its useful life. These attempts have usually been in the form of providing a reinforcement ring about the central aperture on one or both sides of the disk, to prevent the drive spindle from damaging the aperture and thereby rendering the disk unuseable. U.S. Pat. Nos. 4,052,750 (Barber, et al.) 4,370,689 (Davies), 4,387,114 (Conner, et al.), 4,480,282 (Brock, et al.) and 4,539,220 (Martinelli) disclose a flexible disk having a central aperture reinforcement structure. None of the above-mentioned patents, however, addresses the specific problem of precisely centering a reinforcing ring on a disk. When the ring is not concentric with the disk, the appearance of the disk is unfavorable to a user; more importantly, the disk assembly lacks the degree of accuracy that is necessary to prevent misalignment between the drive spindle and the disk.
Even when the reinforcing ring is concentric with the disk, the reinforcement structure of the prior art may suffer from a disadvantage in that an adhesive used to attach the ring to the disk may come into contact with the bonding apparatus during the assembly operation. The adhesive must remain in place or it will foul the contact surface of the bonding apparatus and thus interfere with subsequent bonding operations. This problem is exemplified with the reinforcing structure and method described in the aforementioned U.S. Pat. No. 4,480,282 in which a flexible disk has a central aperture which is slightly greater than the aperture of a reinforcing ring. When the ring and disk are precisely centered with respect to each other, only the ring, which is made of a physically strong non-malleable material, would contact a disk drive spindle. With a disk assembly of this design, it is required that the adhesive be one which hardens quickly and requires only a slight bonding force to set the bond between the ring and disk. To fabricate a floppy disk assembly in accordance with that description, however, it is difficult to prevent the adhesive from adhering to the contact surface of the bonding apparatus. This makes it possible for dirt and other contaminants to adhere to the adhesive on the bonding apparatus and thereby produce dimensional errors or obstacles with respect to the periphery of the central disk drive aperture of disk assemblies produced during subsequent bonding operations.
Furthermore, long term usage of floppy disk assemblies, constructed in accordance with that description or other prior art structures in which the central apertures of the ring and the disk are precisely the same size, results in the adhesive oozing from between those members to project within the area of the central drive aperture. Consequently, in time, a spindle of the reading and writing apparatus driving the floppy disk assembly becomes contaminated with adhesive.
FIG. 1 shows conventional bonding apparatus 10 for positioning and attaching a reinforcing ring 12 to a flexible disk 13. The ring 12, with an adhesive 14 facing downwardly, is arranged around the neck 15 of a suitable force translating mechanism 16, one at a time. Preferably, a vacuum pump (not shown) serves to hold the reinforcing ring 12 pneumatically, as shown diagrammatically by the arrows, against a circular lip 18, which serves to press the ring 12 against the disk 13.
As shown, the disk 13 is placed about a resiliently mounted receiving member 20 centrally disposed in a disk stand 22. Suitable drive means 23 provides for raising and lowering the mechanism 16 relative to the disk stand 22. The mechanism 16 engages and thereby depresses the receiving member 20, to bring the ring 12 into contact with the disk 13. As the mechanism 16 passes through the central aperture of the disk 13, the tapered end of the neck 15 serves to correct any significant misalignment between the center of the disk 13 and the center of the ring 12. When the mechanism is lowered completely, the lip 18 presses the reinforcing ring 12 against the disk 13, whereby the ring is attached to the disk by the adhesive 14 on the downwardly facing side of the ring.
To assist in preventing the adhesive 14 from contacting the apparatus 10 during a bonding operation, the size of the inner diameter of the reinforcing ring 12 is usually somewhat larger than the size of the inner diameter of the disk 13. This feature, however, makes it possible that either the ring 12 and/or the disk 13 is not always positioned laterally in the same position relative to the neck 15 of the mechanism 16. This makes it difficult to obtain consistently good registration between the aperture of the disk 13 and the aperture of the reinforcing ring 12, thereby presenting an appearance of sloppy workmanship. Poor registration can, of course, prevent the centering of the disk 13 precisely on the spindle of its drive mechanism, thereby causing read/write errors relating to the improper indexing of a disk read/write head. Furthermore, poor registration makes it more likely that adhesive will flow between the adjacent faces of the ring 12 and the disk 13 into the area of the central disk drive aperture or into contact with the bonding apparatus 10.